Re: [Boost-users] [BGL] filtered graph missing vertex function

On 9/5/06, Stephan Diederich wrote:

Hi Moritz,

2006/9/5, moritz Hilger : - Zitierten Text anzeigen -

...

is there a particular reason that the filtered graph is missing a vertex_descriptor vertex(vertices_size_type, const& filtered_graph) function? of course this would return exactly the same as the one of the underlying graph, nevertheless it would be handy for code treating filtered graphs the same way as normal ones.

I think the problem here is the return value of the function. If you have a VertexPredicate set, it would be possible that the vertex you specify through the index doesn't exist in the filtered graph. Maybe a null_vertex() could be returned in that case (But, IIRC, that null_vertex() doesn't exist in every graph).

hmm, the null_vertex() function is part of the graph concept ( http://www.boost.org/libs/graph/doc/Graph.html) and should return "a special boost::graph_traits<G>::vertex_descriptor object which does not refer to any vertex of graph object which type is G." so why not return this if the VertexPredicate excludes the requested vertex? cheers, moritz